True irony—for there also is a false one—is the irony of love. It arises out of the feeling of finiteness and one's own limitation, and out of the apparent contradiction between this feeling and the idea of infinity which is involved in all true love. As in actual life and in the love which centers in an earthly object, a good-humored raillery, which amuses itself with some little defect of character, either apparent or real, is not inconsistent with sincerity— not, at least, when both parties have no doubt of each other's affection, and its ardor admits of no increase—but, on the contrary, lends to it an agreeable charm, even so is this true of that other and highest love. Here, too, an apparent, or it may be an actual, but still only insignificant and trivial contradiction, can not destroy the idea on which such a love is based, but, on the contrary, serves rather to confirm and strengthen it. But only there where love has reached the highest purity—has become profoundly confirmed and perfect—does this appearance of contradiction, which is thrown out in an affectionate irony, fail to alloy or weaken all higher and better feeling.
Friedrich von Schlegel, Philosophy of Language, Morrison, tr., p. 382.